JP2013541161A - Lithium titanate battery with reduced gas generation - Google Patents

Abstract

  A method of manufacturing a lithium battery is disclosed. The method can include providing a lithium battery having an operating voltage range, comprising a negative electrode, a positive electrode, and an electrolyte in contact with and between the negative electrode and the positive electrode. The negative electrode can include lithium titanate and the electrolyte can include an additive. The method may also include the step of reducing the additive to form a coating on the surface of the negative electrode in contact with the electrolyte. This reduction step may include the step of overcharging the lithium battery to a voltage that is greater than the upper limit of the operating voltage range and lowering the negative electrode voltage to 0.2-1 V relative to lithium.

Description

Explanation of related applications

  This application is a continuation-in-part of U.S. Patent Application No. 12/015901 filed on January 17, 2008, and U.S. Provisional Patent Application No. 60/880818 filed on January 17, 2007, US Provisional Patent Application No. 60/882126, filed Jan. 19, 2007, and US Provisional Patent Application No. 60/899089, filed Feb. 2, 2007. Based on US patent application Ser. No. 12 / 888,894 filed on Jan. 20, all of the previous applications are hereby expressly cited.

  The present invention relates generally to a method of manufacturing a lithium battery, and more particularly to a method of forming a film on the negative electrode of a lithium battery.

  For example, vehicles such as hybrid vehicles use a number of propulsion systems to provide motive power. The most common hybrid vehicle is a hybrid vehicle that uses both gasoline and electricity, and this hybrid vehicle includes both an internal combustion engine (ICE) and an electric motor. Hybrid vehicles that use both gasoline and electricity use gasoline to run the ICE and use a battery to run the electric motor. Hybrid vehicles that use both gasoline and electricity recharge the battery by acquiring kinetic energy. This kinetic energy can be provided by regenerative braking or from the output of the ICE during cruise or idling. This is in contrast to a pure electric car. The electric vehicle uses a battery that is charged by an external source such as a power supply network or a range extending trailer.

  These batteries generally include a rechargeable lithium-based battery that includes two different electrodes immersed in an ion conducting electrolyte, namely an anode and a cathode, with a separator disposed between the two electrodes. Electrical energy is generated in the cell by an electrochemical reaction that occurs between two different electrodes.

  The greatest demand placed on the battery arises when current must be supplied to operate the electric motor during acceleration. Electric motor amperage requirements will range to hundreds of amperes. Most types of batteries that can supply the required amperage require large capacity, i.e., bulky shipping containers, which results in excessive battery mass and high battery costs. At the same time, such large currents are only needed for a short period, usually a few seconds. Thus, so-called “high power” batteries that deliver large currents in a short period of time are typically ideal for hybrid and pure electric vehicle applications.

  Rechargeable batteries, including rechargeable lithium-based batteries, sometimes characterized as either lithium batteries, lithium ion batteries, or lithium polymer batteries, enable hybrid vehicles to meet performance standards while being economical. It combines the power and cycle life required with high power generation capacity. “High electric power-generating capacity” means that the rechargeable battery is 4 times the energy density of lead acid batteries and 2 to 3 times the energy density of nickel-cadmium and nickel-metal hydride batteries. It means having double energy density. Rechargeable batteries, including lithium-based batteries, also have the potential to be one of the lowest cost battery systems.

Lithium titanate represented by the formula Li ₄ Ti ₅ O ₁₂ (or Li _4/3 Ti _5/3 O ₄ ) is the most promising material for use in rechargeable lithium ion and lithium polymer battery anodes. Is considered one of them. Lithium titanate Li ₄ Ti ₅ O ₁₂ is known from A. Deschanvers et al. Li ₄ Ti ₅ O ₁₂ can function in a reversible electrochemical reaction, as was later published by KM Colbow et al. (Non-Patent Document 2), whereas elemental lithium is such a reversible reaction. There is no ability to do. After detailed research by T. Ozhuku et al. (Non-Patent Document 3), lithium titanate has been considered for use as an anode material for rocking chair type lithium batteries. In fact, Koshiba et al., US Pat. No. 5,677, 199 discloses the use of lithium titanate having various ratios of lithium to titanium in lithium titanate. More specifically, the lithium titanate of Patent Document 1 is of the formula Li _x Ti _y O ₄ and at the cathode of the lithium battery, 0.8 ≦ x ≦ 1.4 and 1.6 ≦ y ≦ 2.2. is there. Patent Document 1 specifies that x + y≈3 basically. In other words, U.S. Pat. No. 6,089,097 includes different ratios of lithium to titanium as long as the total amount of lithium and titanium is about 3 so that there is a stoichiometric amount of lithium and titanium to oxygen. Teaching good. Patent Document 2 such as Thackeray also discloses lithium titanate used as an anode of a lithium battery. The lithium titanate may be a stoichiometric or defective spinel where the lithium distribution can vary from compound to compound.

In addition to the ability to function in reversible electrochemical reactions, Li ₄ Ti ₅ O ₁₂ has other advantages that make this material useful in rechargeable lithium-based batteries. For example, lithium titanate has excellent cycling characteristics due to the unique small volume change of lithium titanate during the charge / discharge process. That is, many cycles of charging and discharging can be performed without deterioration of the battery. The excellent cycle characteristics of this lithium titanate are mainly due to the cubic spinel structure of Li ₄ Ti ₅ O ₁₂ . According to the data of S. Scharner et al. (Non-Patent Document 4), the lattice parameter of the cubic spinel structure (cubic, Sp. Gr. Fd-3m (227)) is 8 in the limit state during charging and discharging. It varies from 3595cm to 8.3538cm. This linear parameter change is equal to a 0.2% volume change. Li ₄ Ti ₅ O ₁₂ has an electrochemical potential of about 1.55 V with respect to elemental lithium, and lithium is inserted into this to insert the inserted lithium titanate represented by the formula Li ₇ Ti ₅ O _12. Which can have a theoretical power generation capacity of up to 175 mA · hr / g.

Another advantage of Li ₄ Ti ₅ O ₁₂ is that it has a flat discharge curve. More specifically, the charging / discharging process of Li ₄ Ti ₅ O ₁₂ occurs in a two-phase system. Li ₄ Ti ₅ O ₁₂ has a spinel structure and converts to Li ₇ Ti ₅ O ₁₂ during charging, which has a regular rock salt structure. As a result, the potential during the charge / discharge process is determined by the electrochemical equilibrium of the Li ₄ Ti ₅ O ₁₂ / Li ₇ Ti ₅ O ₁₂ pair and does not depend on the lithium concentration. This is in contrast to the discharge curves of most other electrode materials of a lithium power supply that maintain the structure during the charge / discharge process. For example, the charge phase transition in most cathode materials such as LiCoO ₂ is predetermined, but there is still an expansion limit for the variable composition Li _x CoO ₂ between these structures. As a result, the potential of the material, such as LiCoO _2, lithium concentration in LiCoO _2, i.e., depends on the state of charge or discharge. Therefore, the discharge curve of a material whose potential depends on the lithium concentration in the material is generally sloped and is often a stepped curve.

There is a general consensus in the art that maintaining good power generation capacity correlates with good electronic conductivity. Li ₄ Ti ₅ O ₁₂ contains titanium with the highest degree of oxidation of +4, which correlates with a very low electronic conductivity. Similar compounds have low electronic conductivity, and many of these compounds are ambiguous dielectrics or insulators. The power generation capacity of Li ₄ Ti ₅ O ₁₂ itself is never ideal. The same applies to the lithium titanate of Patent Documents 1 and 2 described above.

Generally, the electronic conductivity of Li ₄ Ti ₅ O ₁₂ is, M. Nakayama, etc. as disclosed by (non-patent document 5), it is improved by doping the 3d elements in Li ₄ Ti ₅ O _12. For example, the electronic conductivity of Li [Li _{(4-x) / 3} Cr _x Ti _{(5-2x) / 3} ] O ₄ , considered as a solid solution between Li ₄ Ti ₅ O ₁₂ and LiCrTiO ₄ , is Li Better than the electronic conductivity of ₄ Ti ₅ O ₁₂ . However, when the amount of Cr ions substituted for titanium ions in Li ₄ Ti ₅ O ₁₂ is increased, it is reversible compared to Li ₄ Ti ₅ O ₁₂ due to electrochemical inactivity due to the presence of Cr ions. Power generation capacity will be reduced. When Cr ions are present, the ASI decreases and the speed capability increases as compared to the area specific impedance (ASI) and speed capability of Li ₄ Ti ₅ O ₁₂ . This loss of capacity is substantially equal to the substitution of substituted titanium.

Other attempts to replace titanium in lithium titanate show similar drawbacks. For example, replacing titanium in Li ₄ Ti ₅ O ₁₂ with vanadium, manganese, and iron significantly reduces reversible power generation capacity during the first charge / discharge cycle. See Non-Patent Document 6.

  Moreover, the use of lithium titanate has proven difficult due to the generation of gas during use. When gas is generated in a sealed lithium battery, an internal pressure is generated, which can reduce battery efficiency or cause the battery to rupture.

US Pat. No. 5,545,468 US Patent Application Publication No. 2002/0197532

Mater. Res. Bull., V.6, 1971, p.699 J. of Power Sources.v.26, N.3 / 4, May 16, 1989, pp.397-402 J. of Electrochemical Society, v.142, N.5, 1995, pp.1431-1435 J. of Electrochemical Society, v.146, N.3, 1999, pp.857-861 Solid State Ionics, 4.117, I.3-4, 2 February 1999.pp. 265-071 P. Kubiak, A. Garsia, MLAldon, J. Olivier-Fourcade, IE Lippens, J.-C. Jumas "Phase transition in the spinel Li4Ti5O12 induced by lithium insertion. Influence of the substitution Ti / V, Ti / Mn, Ti / Fe "(J. of Power Sources, v. 119-121, June 1, 2003, pp.626-630)

  In view of the above, there remains an opportunity to provide improved lithium titanate to exhibit excellent electronic conductivity while maintaining the reversible power generation capability characteristic of lithium titanate.

  A method of manufacturing a battery is disclosed. The method may include providing a lithium battery having a certain operating voltage range. The lithium battery can include a negative electrode, a positive electrode, and an electrolyte in contact with and between the negative and positive electrodes. The negative electrode can include lithium titanate, the positive electrode can include lithium titanate, or both the negative electrode and the positive electrode can include lithium titanate. The electrolyte can include additives.

  The method can include forming a coating at the interface of the negative electrode in contact with the electrolyte by reducing the additive. This forming step is performed by lowering the voltage of the negative electrode to a range of 0.2 to 1 V with respect to lithium or a range of 0.5 to 0.9 V with respect to lithium while making the lithium battery higher than the upper limit of the operating voltage range. Overcharging to a voltage may be included.

  The duration of the formation process may be sufficient to produce a continuous coating at the negative electrode interface. The lower limit of the operating voltage range may be 1.3V or higher. The electrolyte can decompose at a potential for lithium of 1.5V to 3.0V, and the continuous coating can prevent electrolyte decomposition at voltages ranging from 0 to 4V.

The additive may include an elemental component selected from the group consisting of boron, phosphorus, sulfur, fluorine, carbon, and combinations thereof. This additive includes lithium hexafluorophosphate (LiPF ₆ ), lithium bisoxalate borate (LiBOB), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF) ₃ SO ₃ ), lithium bis (trifluoromethanesulfone) imide (Li (CF ₃ SO ₂ ) ₂ N), lithium tetrafluoroborate (LiBF ₄ ), lithium tetrachloroaluminate (LiAlCl ₄ ), lithium hexafluoroantimonate (LiSbF _6), lithium tetrafluoro (oxalato) phosphate (LiFOP), lithium difluoro (oxalato) borate (LiFOB), Hosufezen, CO _2, phosphate esters, borate esters, and from the group consisting of water It may be additive-option. The additive can be lithium bisoxalate borate (LiBOB), phosphazene, or a mixture of both.

  The additive may include at least one chelate borate. Additives: carbonate, chloroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, sulfite, ethylene sulfite, propane sulfone, propylene sulfite, butyrolactone, phenyl ethylene carbonate, phenyl vinylene carbonate, catechol carbonate, vinyl acetate, vinyl ethylene carbonate, sulfurous acid It can be an additive selected from the group consisting of dimethyl, fluoroethylene carbonate, trifluoropropylene carbonate, bromogammabutyrolactone, fluorogammabutyrolactone, and combinations thereof.

Lithium titanate has the formula:
Li ₄ Ti ₅ O _12-x
In which x is greater than 0 and less than 12. The value of x can be greater than 0 and less than 0.02. The average valence of titanium in the lithium titanate can be less than 4.

The negative electrode can include a first lithium titanate having the following formula: Li ₄ Ti ₅ O ₁₂ and a second lithium titanate different from the first lithium titanate. The second lithium titanate can be of the formula: Li ₄ Ti ₅ O _12-x where x is greater than 0 and less than 12. The amount of the second lithium titanate in the negative electrode can be greater than the amount of the first lithium titanate in the negative electrode. The negative electrode contains at least 10% by mass of second lithium titanate (Li ₄ Ti ₅ O _12-x ) greater than the first lithium titanate based on the total amount of the first and second lithium titanates. It does not matter. In other words, the proportion of the second lithium titanate (Li ₄ Ti ₅ O _12-x ) based on the total amount of the first and second lithium titanates is at least 55% by weight, or at least 65% by weight, or at least 75%. It can be mass%.

The lithium battery may also include a gas absorbent. Gas absorbent, ZnO, NaAlO _2, may be selected from the group consisting of silicon, and combinations thereof. A negative electrode may contain the gas absorbent. The lithium battery can also include a separator, and the gas absorbent is retained by the separator.

Other advantages of the present invention will be readily appreciated and will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.
Illustration of rechargeable battery including lithium-based battery Explanatory drawing of the vehicle including the rechargeable battery of FIG. Lithium titanate composition-valence graph showing the relationship of the ratio of lithium to titanium in lithium titanate to the valence of titanium in lithium titanate, diamonds indicate spinel structure, squares indicate non-spinel structure The black symbol indicates lithium titanate containing inserted lithium ions Explanatory drawing of the battery before forming the coating on the negative electrode Explanatory drawing of the battery after forming the coating on the negative electrode X-ray diffraction spectrum for prior art conventional Li ₄ Ti ₅ O ₁₂ synthesized according to composition example 1 in Table 2 X-ray diffraction spectrum for Li ₄ Ti ₅ O _11.985 of the present invention synthesized according to Example 1 in Table 1. Was synthesized according to Example 1 of Table 1, concerning Li ₄ Ti ₅ O _11.985 of the present invention was measured by four-point probe method, a graph showing the dependence of log (sigma) for 1 / T A Li ₄ Ti ₅ O ₁₂ gas mixture of H ₂ / argon (4.81% by volume of H ₂₎ showing the dependence of the H ₂ concentration on the temperature during heating at a constant temperature increase of 2.5 ° C./min. ₂ ) Reaction curve of sintering process reduced by Reaction curve of the sintering process of FIG. 7 in log (x) coordinates for 1 / T, where _x is x in Li ₄ Ti ₅ O _12-x Graph showing the dependence of power generation capacity (mAh) on the number of cycles for a battery comprising an electrode with Li ₄ Ti ₅ O _12-x of the present invention, where the counter electrode is lithium metal Graph showing the initial discharge of a battery comprising an electrode with Li ₄ Ti ₅ O _12-x of the present invention, wherein the counter electrode is lithium metal Graph showing the second charge of a battery comprising an electrode with Li ₄ Ti ₅ O _12-x of the present invention, wherein the counter electrode is lithium metal Graph showing the 382nd discharge of a battery comprising an electrode with Li ₄ Ti ₅ O _12-x of the present invention, wherein the counter electrode is lithium metal. Graph showing the 382nd charge of a battery comprising an electrode with Li ₄ Ti ₅ O _12-x of the present invention, wherein the counter electrode is lithium metal A and B indicate that little or no gas was produced in the battery of the present invention, whereas a considerable amount of gas was produced in the comparative battery, respectively. The side of a battery is shown.

  The lithium titanate of the present invention is useful in lithium batteries. The lithium-based battery containing the lithium titanate of the present invention is used for many applications, but is particularly useful in a rechargeable battery of a vehicle 10 such as a hybrid vehicle or an electric vehicle 10. However, it should be recognized that this lithium-based battery may be used for non-rechargeable batteries. The rechargeable battery is a power source for the electric motor of the vehicle 10. Lithium-based batteries will also be known as lithium ion batteries. Moreover, lithium ion batteries are also called secondary batteries and vice versa. In many cases, lithium ion batteries are specifically referred to as rocking chair type batteries, as lithium ions move between the positive and negative electrodes, as further described below.

  Lithium-based batteries include an electrolyte, an anode, and a cathode. It should be recognized that the descriptions of the anode and cathode are interchangeable with the descriptions of the electrodes in the description of the invention. Lithium-based battery electrolytes are generally organic electrolytes and / or non-aqueous lithium ion conducting electrolytes and are known in the art. Suitable electrolytes are described in further detail below for the purposes of the present invention. In general, at least one of the anode and cathode comprises the lithium titanate of the present invention. For example, a lithium-based battery may be further defined as a lithium battery, where the cathode comprises the lithium titanate of the present invention. The lithium titanate is typically present in the cathode in an amount of at least 80 parts by weight, more typically 80 to 90 parts by weight, and most typically about 82 parts by weight, based on the total weight of the cathode. Exists. In addition to lithium titanate, the cathode of a lithium battery typically includes a conductive agent such as carbon black, along with a binder such as polyvinylidene fluoride (PVDF), which can constitute the remainder of the cathode. More particularly, the carbon black is typically present in an amount of 8 to 10 parts by weight, more typically about 8 parts by weight, based on the total weight of the cathode, and the binder is typically present in the cathode. It is present in an amount of 8 to 12 parts by weight, more typically about 10 parts by weight, based on the total weight. The anode of a lithium battery is typically lithium metal or a lithium alloy with magnesium or aluminum.

  Alternatively, a lithium-based battery or battery may be further defined as one of a lithium ion battery and a lithium polymer battery, wherein the anode comprises the lithium titanate of the present invention in the amounts described above.

  When used in rechargeable batteries for applications including, but not limited to, hybrid vehicles or electric vehicles 10, the batteries are typically used in battery packs, represented at 14 in FIGS. . The battery pack 14 typically includes four rows of batteries that are interconnected and extend along each row in an overlapping relationship. Each row typically includes five stacks of batteries. However, it should be recognized that other configurations of batteries may be used in the battery pack 14. Other configuration batteries and batteries will be further described.

  As is known in the art, a rechargeable battery typically includes a plurality of battery packs 14 connected in circuit to provide sufficient energy to power the vehicle 10. As shown in FIGS. 1 and 2, the circuit is composed of a switch 18 and a battery management system 20 installed in the circuit 16. The battery management system 20 includes a switch management and interface circuit 22 for managing energy use from the batteries in the battery pack 14 and charging thereof.

The lithium titanate of the present invention has the following formula:
Li ₄ Ti ₅ O _12-x
Where x is greater than 0 and less than 12. Typically, 0 <x <0.02. In other words, the lithium titanate of the present invention is oxygen deficient, which is superior to the above-described lithium titanate of the above formula that is not oxygen deficient, such as Li ₄ Ti ₅ O _12. Have At the same time, the concentration of lithium in the lithium titanate of the present invention remains the same as that for lithium titanate that is not oxygen deficient. As a result, the predicted reversible power generation capacity of the lithium titanate of the present invention remains the same as the reversible power generation capacity of lithium titanate containing a stoichiometric amount of oxygen.

The effect on electronic conductivity as a result of oxygen deficiency is due to the change in oxidation state, ie, the valence of titanium in lithium titanate. More specifically, lithium titanate containing titanium atoms in the +3 oxidation state exhibits high electronic conductivity, which is characteristic of metal-like materials, whereas lithium titanate containing titanium atoms in the +4 oxidation state is dielectric. It exhibits low electronic conductivity, which is a characteristic of the material. Referring to FIG. 3, the various lithium titanate oxidation states are shown on the vertical axis as v (Ti), ie, the valence of titanium. Thus, FIG. 3 shows the relative electronic conductivity of various lithium titanates at various states of insertion, with higher v (Ti) correlating with lower electronic conductivity. Li ₄ Ti ₅ O ₁₂ is an example of lithium titanate having titanium atoms in the +4 oxidation state.

During electrochemical insertion or charging of conventional Li ₄ Ti ₅ O ₁₂ , a phase transition from spinel to “rock salt” type occurs, where three lithium atoms are inserted into the conventional Li ₄ Ti ₅ O ₁₂ As a result, Li ₇ Ti ₅ O ₁₂ is produced. Li ₇ Ti ₅ O ₁₂ is shown in FIG. 3 and has the following formula:
Li ₄ Ti ₅ O ₁₂ + zLi ⁺ + ze ⁻ → (1-z / 3) Li ₄ Ti ⁴⁺ ₅ O ₁₂ + z / 3Li ₇ Ti ⁴⁺ ₂ Ti ³⁺ ₃ O ₁₂
(In the formula, z represents the number of lithium atoms inserted in Li ₄ Ti ₅ O ₁₂ )
As represented by, for conversion of a conventional Li ₄ Ti ₅ titanium atom in O ₁₂ from +4 oxidation state during insertion into the oxidation state of +3, higher than the conventional Li ₄ Ti ₅ O ₁₂ Has electronic conductivity. Therefore, the conventional Li ₄ Ti ₅ O ₁₂ exhibits various electronic conductivity based on the state of insertion, and the difference in the electronic conductivity between the conventional Li ₄ Ti ₅ O ₁₂ and Li ₇ Ti ₅ O ₁₂ is different. Because of this, high electronic conductivity will exist during insertion and discharge. The poor electronic conductivity of conventional Li ₄ Ti ₅ O ₁₂ results in the initial “training” of the battery, due to the low current as well as the prevention of full charge. These environments severely limit the opportunity to use conventional Li ₄ Ti ₅ O ₁₂ for high rate applications.

Surprisingly, according to the present invention, it has been found that the following relationship exists:
Li ₄ Ti ₅ O ₁₂ + δH ₂ → Li ₄ Ti ⁴⁺ _5-2 Ti ³⁺ ₂ O _12-δ + δH ₂ O ↑

As a result of charge compensation, substantially reducing the Li ₄ Ti ₅ O ₁₂ to form Li ₄ Ti ₅ O _12-x while maintaining the same number of lithium and titanium atoms in the lithium titanate. A conversion of the titanium atom in ₄ Ti ₅ O ₁₂ from the +4 oxidation state to the +3 oxidation state results. In other words, the average valence of titanium in the lithium titanate of the present invention is less than 4. The practical result of the above-described discovery is that lithium and titanate, in contrast to conventional Li ₄ Ti ₅ O ₁₂ , which exhibits an electronic conductivity close to that of the dielectric material before charging, It does not show a very dramatic change in electronic conductivity at all stages, so different areas of Li ₄ Ti ₅ O _12-x and Li ₇ Ti ₅ O _12-x are different from conventional Li ₄ Ti ₅ O ₁₂ In comparison, it represents a more uniform medium for charging and discharging processes, which is advantageous for high rate applications.

Since the same number of electrochemically active lithium and titanium atoms are present in Li ₄ Ti ₅ O ₁₂ , the predicted power generation capacity is that for Li ₄ Ti ₅ O _12-x The same as for Li ₄ Ti ₅ O ₁₂ . Li ₄ Ti ₅ O _12-x also maintains the same spinel structure as Li ₄ Ti ₅ O ₁₂ with excellent cycle characteristics. As described above, typically 0 <x <0.02 in order to maintain lithium titanate having the same spinel structure as Li ₄ Ti ₅ O ₁₂ . More specifically, referring to FIG. 3, since the lithium titanate of the present invention has an oxygen deficiency, Li ₄ Ti ₅ O _12-x is converted into an oxidation state of +4 of a titanium atom in Li ₄ Ti ₅ O _12. 3 is shifted to the position represented by “A” in FIG. 3, and the position represented by “B” represents the insertion state of Li ₄ Ti ₅ O _12-x. . The value of x is limited in order to maintain the same spinel structure as Li ₄ Ti ₅ O ₁₂ . This is because if the amount of titanium in the +3 oxidation state is too large, lithium titanate having the structure Li ₂ Ti ₃ O ₇ is formed. Li ₂ Ti ₃ O ₇ has an orthorhombic crystal structure with a space group Pbnm (62). Li ₂ Ti ₃ O ₇ may be suitable for certain applications, but the spinel structure of Li ₄ Ti ₅ O ₁₂ contains more lithium in its structure than can be inserted into Li ₂ Ti ₃ O _7. Due to its ability to be inserted, and Li ₄ Ti ₅ O ₁₂ shows a small volume change from 3.2595 Å to 8.5538 Å between the inserted and uninserted states, which gives excellent cycling characteristics Because of the fact that

The method of forming Li ₄ Ti ₅ O _12-x includes providing a mixture of titanium dioxide and a lithium-based component. Exemplary mixtures can include a powder or particulate mixture of titanium dioxide, a lithium-based component, and any additional components (eg, binders and gas absorbers). Titanium dioxide can be used in both rutile and anatase forms, as well as any form of titanium dioxide-hydroxide (such as Ti (OH) _2x O _2-x ). Any lithium-based component typically used to form Li ₄ Ti ₅ O ₁₂ may be used. Typically, the lithium-based component is selected from the group consisting of lithium carbonate, lithium hydroxide, lithium oxide, and combinations thereof, and this lithium-based component is typically at least 99% pure. Lithium salts or lithium organic acids can be used. Typically, the lithium-based component and titanium oxide are present in the mixture in the amounts necessary to ensure the atomic ratio Li / Ti = 0.8 in the final lithium titanate of the present invention.

  A mixture containing titanium dioxide and a lithium-based component is sintered in a gaseous atmosphere containing a reducing agent to form lithium titanate. More particularly, the mixture is at least 450 ° C., more typically from about 500 to 925 ° C., most typically about 700 minutes, over a period of at least 30 minutes, more typically from about 60 to about 180 minutes. To about 920 ° C.

This reducing agent may be any agent capable of reducing oxygen in Li ₄ Ti ₅ O ₁₂ and is typically selected from the group of hydrogen, hydrocarbons, carbon monoxide and combinations thereof. The The reducing agent is typically at least 0.1% by volume, more typically about 1 to about 100, in order to sufficiently reduce Li ₄ Ti ₅ O ₁₂ to form Li ₄ Ti ₅ O _12-x. Present in a gaseous atmosphere at a concentration of volume percent.

The gaseous atmosphere typically includes, in addition to the reducing agent, another gas selected from the group of inert gas, inert gas, and combinations thereof. Any inert gas, such as a noble gas, may be used to prevent unwanted side reactions during sintering and to prevent introduction of impurities into the Li ₄ Ti ₅ O _12-x . An inert gas that may be used is, for example, pure nitrogen.

  Another embodiment of the invention will now be described. In particular, other types of lithium batteries (or lithium ion batteries) and lithium batteries (or lithium ion batteries) are also provided by the method of the present invention. Typically, as described above, a lithium battery or battery includes a positive electrode (ie, anode) and a negative electrode (ie, cathode). In general, the positive and negative electrodes include materials that can occlude lithium or lithium ions, such as those previously described and exemplified.

  As shown in FIGS. 4 and 5, in one embodiment, the negative electrode 112 is an active material capable of reversibly occluding lithium species, eg, lithium transition metal oxides, metal current collector material 113, eg, copper foil. , An adhesive (or binder), such as PVDF, styrene butadiene rubber (SBR), etc., and optionally a plate containing a conductive agent / conductive aid such as carbon black.

  In one embodiment, the positive electrode 116 is a plate that includes an active material capable of occluding lithium species, a metal current collector 117, an adhesive, and optionally a conductive aid. The active material of the positive electrode 116 may be the same as or different from the active material of the negative electrode 112. Further, the metal current collecting material 117 of the positive electrode 116 may be the same as or different from the metal current collecting material 113 of the negative electrode 112. Furthermore, the adhesive of the positive electrode 116 may be the same as or different from the adhesive of the negative electrode 112. When used, the conductive auxiliary of the positive electrode 116 may be the same as or different from the conductive auxiliary of the negative electrode 112.

Examples of suitable lithium transition metal oxides include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFePO ₄ , and combinations thereof for the purposes of the present invention. As will be appreciated by those skilled in the art, if desired, titanium, aluminum, magnesium, nickel, manganese, and combinations thereof may be used to dope transition metal sites. The positive electrode and / or the negative electrode may have other shapes known in the art other than the plate shape, such as a wound / wound structure and / or a laminated / laminated structure.

The lithium battery or battery 100 also includes an electrolyte 118 as described above. Typically, the electrolyte 118 can include a lithium salt dissolved in a non-aqueous solvent. Non-aqueous solvents may include those that are in the form of a complete liquid, a complete solid, or a gel between the complete liquid and the complete solid. Suitable liquid electrolytes include, but are not limited to, alkyl carbonates such as propylene carbonate and ethylene carbonate, dialkyl carbonates, cyclic ethers, cyclic esters, glymes, lactones, formates, esters, sulfones, nitrates, oxazolas Oxazoladione, and combinations thereof. Suitable polymers used as the solid electrolyte include, but are not limited to, polyethylene oxide (PEO), polymethylene-polyethylene oxide (MPEO), PVDF, polyphosphazene (PPE), and combinations thereof. Suitable lithium salts include, but are not limited to, LiPF ₆ , LiClO ₄ , LiSCN, LiAlCl ₄ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ include _{LiO 3 SCF 2 CF 3, LiC} 6 F 5 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, and combinations thereof. It should be appreciated that the electrolyte 118 may include various combinations of the components previously described and illustrated, as will be appreciated by those skilled in the art.

  When using liquid and / or gel type electrolytes, the separator 124 is typically disposed between the positive electrode 116 and the negative electrode 112, and the electrolyte 118 is held by the separator 124 to prevent short circuits within the battery 100. Is done. Separator 124 may be any type of separator known in the art, for example, a porous polymer separator. In one embodiment, the lithium ion battery has a negative electrode plate, a positive electrode plate, and a separator disposed between the wound structure and the laminated structure. The electrolyte is poured between them, and the battery is placed in a metal case or metal laminated case 111 and sealed.

  As described above, the copper foil is generally used as the current collecting material 113 of the negative electrode plate 112. In general, to prepare the negative electrode plate, a slurry is applied onto a copper foil, dried and pressed. The slurry includes an active material, an adhesive, and optionally a conductive aid. It should be appreciated that the current collector described above may be manufactured from other metals and / or alloys including, but not limited to, nickel, titanium, stainless steel, aluminum, and copper; Copper is generally preferred as described above. In addition, the current collector 113 can be manufactured in various forms such as plates, small pieces, foils, meshes, nets, and metal foam plates.

Typically, the lithium titanate of the present invention described and exemplified above, ie Li ₄ Ti ₅ O _12-x, is used as the active material for the negative electrode. As described above (or implied), lithium titanate has excellent cycle characteristics due to the small volume change associated with charging. In modern lithium batteries and batteries, for example, a film is generally formed on the surface of graphite, which is used as the negative electrode of the battery or battery, by reductive decomposition of the electrolyte. Such a membrane inhibits the electrolyte from further degradation. However, lithium titanate is generally considered not to have such a film formed over the surface of graphite. Therefore, when the surface potential of lithium titanate drops below 1.2 V (relative to Li + Li), it is considered that a large amount of electrolyte generates gas that includes reductive decomposition products and adversely affects cycle characteristics. It is also conceivable that the binder can be reduced when the surface potential of lithium titanate drops below 1.2V. To alleviate some of these potential challenges, the negative electrode typically needs to have the same or higher capacity as the positive electrode when using lithium titanate.

The present invention also provides active materials suitable for use in lithium batteries such as those described herein. The active material includes a lithium titanate having a surface and a material disposed on the surface of the lithium titanate. This material is generally non-reactive to the electrolyte within the range of potentials from 0V to 4V lithium while the active material is in the presence of the electrolyte. Lithium titanate is the one described and exemplified above, namely Li ₄ Ti ₅ O _12-x . Typically, once the material is formed, it prevents the electrolyte from degrading at the surface of the material. The material can also be referred to as a surface membrane or membrane.

  A method of manufacturing a battery 100 having a coating 114 on the negative electrode 112 is also disclosed. 4 and 5 show the battery 100 before and after the manufacturing process, respectively.

  The method can include providing a lithium battery 100 that includes a negative electrode 112, a positive electrode 116, and an electrolyte 118 in contact with and between the negative electrode 112 and the positive electrode 116. The negative electrode 112 can include lithium titanate, the positive electrode 116 can include lithium titanate, or both the negative electrode 112 and the positive electrode 116 can include lithium titanate. The electrolyte 118 can include additives.

  The method may also include forming a coating 114 at the interface 120 of the negative electrode 112 in contact with the electrolyte 118 by reducing the additive. The lithium battery 100 may have a certain operating voltage range, and the forming step includes overcharging the lithium battery to a voltage higher than the upper limit of the operating voltage range while lowering the voltage of the negative electrode 112 below the lower limit of the operating voltage range. Can be included. For example, the voltage of the negative electrode 112 can drop to a range of 0.2 to 1 V with respect to lithium or a range of 0.5 to 0.9 V with respect to lithium.

  The upper limit of the operating voltage range can be 2.8V, or 3.2V, or 3.5V. The lower limit of the operating range can be 1V, or 1.2V, or 1.3V. As used herein, the operating voltage range is the range of voltages designed to operate a lithium battery during standard use by the end user.

  The duration of the formation process may be sufficient to produce a continuous coating 114 at the interface 120 of the negative electrode 112. The coating 114 can include the reduction product of the additive in the electrolyte 118. The lower limit of the operating voltage range may be 1.3V or higher. The electrolyte 118 can decompose at a potential for lithium of 1.5V to 3.0V, and the continuous coating 114 can prevent decomposition of the electrolyte 118 at voltages ranging from 0 to 4V.

The additive may include an elemental component selected from the group consisting of boron, phosphorus, sulfur, fluorine, carbon, boron, and combinations thereof. This additive includes lithium hexafluorophosphate (LiPF ₆ ), lithium bisoxalate borate (LiBOB), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF) ₃ SO ₃ ), lithium bis (trifluoromethanesulfone) imide (Li (CF ₃ SO ₂ ) ₂ N), lithium tetrafluoroborate (LiBF ₄ ), lithium tetrachloroaluminate (LiAlCl ₄ ), lithium hexafluoroantimonate (LiSbF _6), lithium tetrafluoro (oxalato) phosphate (LiFOP), lithium difluoro (oxalato) borate (LiFOB), Hosufezen, CO _2, phosphate esters, borate esters, and from the group consisting of water It may be additive-option. The additive can be lithium bisoxalate borate (LiBOB), phosphazene, or a mixture of both.

  The additive may include at least one chelate borate. Additives: carbonate, chloroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, sulfite, ethylene sulfite, propane sulfone, propylene sulfite, butyrolactone, phenyl ethylene carbonate, phenyl vinylene carbonate, catechol carbonate, vinyl acetate, vinyl ethylene carbonate, sulfurous acid An additive selected from the group consisting of dimethyl, fluoroethylene carbonate, trifluoropropylene carbonate, bromogamma butyrolactone, fluorogamma butyrolactone, and combinations thereof may be included. One or more additives may be present in the electrolyte 118.

Lithium titanate has the formula:
Li ₄ Ti ₅ O _12-x
In which x is greater than 0 and less than 12. The value of x can be greater than 0 and less than 0.02. The average valence of titanium in the lithium titanate can be less than 4.

The negative electrode 112 may include a first lithium titanate having the following formula: Li ₄ Ti ₅ O ₁₂ and a second lithium titanate different from the first lithium titanate. The second lithium titanate can be of the formula: Li ₄ Ti ₅ O _12-x where x is greater than 0 and less than 12. The amount of the second lithium titanate in the negative electrode 112 can be larger than the amount of the first lithium titanate in the negative electrode. The negative electrode 112 may include a second lithium titanate that is at least 10% by weight greater than the first lithium titanate, based on the total amount of the first and second lithium titanates.

The lithium battery 100 can also include a gas absorbent 122. The gas absorbent 122 can be selected from the group consisting of ZnO, NaAlO ₂ , silicon, and combinations thereof. The negative electrode 112 may include the gas absorbent 122. The gas absorbent 122 can be in the form of a powder or particulate. The lithium battery may also include a separator 124, and the gas absorbent 122 is retained by the separator 124.

In one embodiment, the lithium battery of the present invention comprises at least two electrodes, each containing lithium titanate, eg, Li ₄ Ti ₅ O _12-x, as described and exemplified above. This lithium battery has an electrode potential at typical operating conditions of 1.3 V, ie, not dropping below the lower limit of the operating voltage range. In another embodiment, the lithium battery of the present invention is at a potential relative to the lithium titanate, eg, Li ₄ Ti ₅ O _12-x , 1.5V to 3.0V lithium described and exemplified above. An electrolyte 118 to be decomposed and a surface film 114 disposed on the lithium titanate are provided. As described above, the surface film 114 is formed as a reduction product of the electrolyte 118, the electrolyte additive, or both. The surface film 114 prevents further decomposition of the electrolyte 118 by preventing direct contact between the electrolyte 118 and the negative electrode 112. In one embodiment, the electrolyte 118 includes lithium bis (oxalate) borate (LiBOB) as an additive. It should be appreciated that other suitable additives may be used in addition to or instead of LiBOB as long as the surface film 114 is formed.

The present invention also provides a lithium battery comprising at least one electrode comprising lithium titanate, such as Li ₄ Ti ₅ O _12-x , as previously described and exemplified. In one embodiment, the lithium battery comprises at least two electrodes, each containing lithium titanate, eg, Li ₄ Ti ₅ O _12-x, as described and exemplified above. In any of the embodiments, the lithium battery further includes a non-fluorine-based binder, that is, a binder that does not contain fluorine in its configuration. Suitable non-fluorinated binders include, but are not limited to, the previously described and exemplified binders such as styrene butadiene rubber (SBR), which are not limited to the following for the purposes of the present invention. In these embodiments, non-fluorine binders are typically used in the electrodes described and exemplified above.

In some embodiments, the electrode includes a first lithium titanate and a second lithium titanate that is different from the first lithium titanate. The first lithium titanate is of the formula Li ₄ Ti ₅ O ₁₂ as previously described, and the second lithium titanate is of the present invention as described and exemplified above. That is, Li ₄ Ti ₅ O _12-x . In certain embodiments, the second lithium titanate is disposed on at least a portion of the surface of the electrode, more preferably on a majority of the surface of the electrode, and most preferably on the entire surface of the electrode. Be placed. Accordingly, the second lithium titanate is typically present in the electrode in an amount that is greater than the amount of the first lithium titanate. For example, in certain embodiments, the electrode includes at least 10% by weight of the second lithium titanate relative to the first lithium titanate, based on the weight of the first and second lithium titanates. Furthermore, the catalytic action of titanium can be reduced, and the decomposition of the binder and electrolyte is using a second lithium titanate, ie Li ₄ Ti ₅ O _12-x , as previously described and illustrated. Can be avoided. Furthermore, with regard to charging, by using the second lithium titanate instead of the first lithium titanate, an excessively large drop in the negative electrode potential is avoided.

In certain embodiments as described above, fluorine-type or fluorine-based binders, i.e. binders having fluorine in their construction, such as PVDF, PTFE, etc., are considered particularly vulnerable to reduction, so Non-fluorinated binders are used. For example, the fluorine-based binder may be decomposed to generate, for example, hydrogen fluoride (HF). HF can be a highly corrosive compound, as understood in the art, and is known to be harmful to a battery or battery when present therein. When such a gas is formed by using a fluorine-based binder or the like, the battery can be prevented from expanding by including a substance that adsorbs the gas decomposed by lithium titanate in the battery. . Specifically, the present invention further provides a lithium battery comprising a lithium titanate, such as Li ₄ Ti ₅ O _12-x , and a gas absorbent 122 as previously described and exemplified. Examples of suitable gas absorbents 122 include, but are not limited to, ZnO, NaAlO ₂ , silicon, and combinations thereof for the purposes of the present invention. The gas absorbent 122 can be held by the separator 124 when used. In general, lithium titanate and gas absorbent 122 are mixed to form electrodes 112 and 116. The lithium titanate and the gas absorbent 122 can be mixed in the form of fine particles or powder. As described above, the battery typically includes a case, so that the gas absorbent can be retained by the case 111 in addition to the separator 124 when used.

The present invention further provides a battery module (or pack) comprising a plurality of lithium batteries, such as those previously described and exemplified. Each of the lithium batteries has a soft outer package and is assembled in an environment where the moisture content in the environment is controlled. The lithium battery typically includes lithium titanate, ie, Li ₄ Ti ₅ O _12-x , described and exemplified above. In one embodiment, the battery module comprises at least 10 lithium batteries. Lithium batteries are typically assembled together in a structure and may be arranged in various structures relative to each other, such as those described and illustrated above. The environment is typically a drying room to properly maintain low levels of moisture during the assembly of the battery, battery, and / or battery module.

  The battery module generally has a seal for sealing the lithium battery and preventing water from entering the battery module and / or the lithium battery. Various methods may be used to form the seal. For example, welding, clamping, and / or heat sealing may be used. In general, a weld seal, such as a weld seal, provides the best sealing performance for the battery module. Heat seal methods, such as those typically used to seal metal laminate soft packages, are generally simple processes and may be used. Suitable examples of flexible outer packages include, but are not limited to, plastics, typically metals laminated with polyolefins such as polypropylene, polyethylene, etc. for purposes of the present invention. Suitable metals such as aluminum are known in the art for the purposes of the present invention. By using various types and thicknesses of plastic, the amount of metal used in the soft outer package can be reduced, thereby reducing the mass and possibly cost of the battery module. Mass is a particularly important concern for hybrid electric vehicle (HEV) applications.

In these embodiments, it is important that water does not enter or break the seal during use of the battery module or during an operable lifetime. As is generally understood in the art, water can have various deleterious effects on battery modules. Specifically, water can react with the electrolyte and produce undesirable reaction products. For example, if the electrolyte includes a fluorinated electrolyte, such as LiPF ₆ , HF can be formed by reaction with water, which causes problems as described and explained above. The same reaction will occur if a fluorinated binder is used. As is understood in the art, other side reactions involving water can also occur. For example, lithium metal can be deactivated by contact with water. To alleviate these problems, non-fluorine electrolytes and binders can generally be used. Water can be controlled so that it is very low in the components used to make batteries and battery modules, for example, if water is present in the electrolyte, it is at least in an amount of, for example, ppm. The following can be maintained. Prior to assembly of the battery module, the other components can be dried. Since long-term reliability is particularly important for HEV applications, sealing performance and strength are critical.

  The following examples are intended to illustrate but not limit the invention.

The lithium titanate of the present invention having the formula Li ₄ Ti ₅ O _12-x is formed according to the method of the present invention described above. More specifically, conventional Li ₄ Ti ₅ O ₁₂ is first formed by preparing a mixture containing titanium dioxide and a lithium-based compound. This mixture is prepared by introducing titanium dioxide and a lithium-based compound into the container in the amounts shown in Table 1. In order to mix titanium dioxide and lithium compound and ensure sufficient mixing of titanium dioxide and lithium compound, the particle size is unimodal distribution until the particle size is less than 5 μm, more preferably less than 2 μm. Using distribution measurements, mill in a ball mill at a rotational speed of at least 150 rpm for a period of about 60 minutes. The mixture is then sintered in the gaseous atmosphere produced by the gas or mixed gas at a constant flow rate at the temperature and time shown in Table 1. This gas or gas mixture contains the amount of reducing agent and inert gas or inert gas shown in Table 1. The resulting lithium titanate has the formula Li ₄ Ti ₅ O _12-x where 0 <x <0.02. Related properties of the lithium titanate of the present invention are also included in Table 1 below.

The lithium-based component A is Li ₂ CO ₃ .

  The lithium-based component B is LiOH.

Reducing agent A is H _2.

The reducing agent B is CH ₄ (methane).

  The reducing agent C is CO (carbon monoxide).

  Inert gas A is argon.

The inert gas B is N ₂ (nitrogen).

A conventional lithium titanate having the comparative formula Li ₄ Ti ₅ O ₁₂ is formed as described above. However, no reducing agent is present in the gaseous atmosphere. The amounts of ingredients used to form the conventional lithium titanate are shown in Table 2 below, along with the relevant properties of the conventional lithium titanate.

Results Regarding the reversible power generation capacity and electronic conductivity of the example and the comparative example, the lithium titanate of the present invention is higher than the conventional lithium titanate of the comparative example while showing a higher reversible power generation capacity. It is clear that it exhibits electronic conductivity.

Specifically, an XRD spectrum is received by an X-ray diffractometer Bruker D4 with CuKα radiation by a Sol-X detector. All samples listed in Tables 1 and 2 give clear spectra corresponding to the cubic structure (Sp. Gr. Fd-3m (227)). There is a small amount of residual TiO ₂ (0.5%) in most samples. Using full profile analysis, conventional structural models (eg S. Scharner, W. Wepner, P. Schmid-Beurmann, Evidence of Two-Phase Formation upon Lithium insertion into the Li _1.33 Ti _1.67 O ₄ Spinel, Journal of (see the electrochmical Society, V.146, E.3, pp.857-861, 1999), the parameter (a) of the cubic crystal lattice was calculated and is shown in Tables 1 and 2. A typical spectrum for the prior art Li ₄ Ti ₅ O ₁₂ represented by Comparative Examples 1 and 2 and a typical spectrum for the Li ₄ Ti ₅ O _11.985 of the present invention represented by Example 2 respectively. It is shown in FIGS.

The electronic conductivity of the examples is measured on 20 mm diameter, 2-3 mm thick pellets pressed and tempered with powder samples under synthesis conditions until equilibrium is reached. The measurement is performed by a four-terminal probe method with a direct current at a potential of 90 volts. Attempts to receive reliable data for the Li ₄ Ti ₅ O ₁₂ sample (Comparative Examples 1 and 2 in Table 2) are unsuccessful. This is because the electronic conductivity of these samples is very close to the lower measurement limit of this method. Therefore, only the number of digits of electronic conductivity is deterministic. The measurement results for Li ₄ Ti ₅ O _11.985 synthesized according to Example 2 in Table 1 in a narrow temperature range of approximately room temperature are shown in FIG. The main cause of measurement discrepancies is the nature of the compressed powder sample with significant porosity, as well as proximity and contact effects to the grain boundaries.

The reaction rate of the sintering process for reducing Li ₄ Ti ₅ O ₁₂ was tested by a temperature controlled reduction method. During linear heating of the sample under a gaseous atmosphere containing a reducing gas, the gas concentration after the sample has flowed too much is measured. Referring to FIG. 9, the dependence of the concentration of hydrogen, ie, the reducing agent, on the temperature of Li ₄ Ti ₅ O ₁₂ is shown. The difference between the initial concentration of hydrogen and the concentration of hydrogen after the gaseous atmosphere has flowed past the sample gives the amount of hydrogen used in the sintering process. The integration of this curve allows the value of _x in the formula Li ₄ Ti ₅ O _12-x to be calculated as a function of temperature using the sample mass and mixed gas flow rate values. The reduction during the sintering process becomes perceptible after 450 ° C. and proceeds smoothly to 925 ° C. FIG. 10 shows the dependence of the logarithm of _x in the formula Li ₄ Ti ₅ O _{12-x on} the inverse absolute temperature (Kelvin). This curve has Arrhenius-like characteristics and is close to a straight line in the temperature range of 500 ° C. <T <925 ° C.

FIG. 11 shows that lithium-based batteries containing Li ₄ Ti ₅ O _12-x maintain power generation capacity after many cycles, and FIGS. 12-15 show even after many charge / discharge cycles. , Li ₄ Ti ₅ O _12-x shows a flat charge / discharge curve.

Example 1-Gas Generation Comparison This example evaluates the difference in gas generation between a battery manufactured using conventional forming techniques and a battery manufactured using the techniques described herein. To do. The comparative battery used a standard electrolyte with a composition of 1.2 M LiPF ₆ in EC / PC / EMC [25/5/70], whereas the battery of the present invention used EC / PC / EMC. An improved electrolyte with a composition of 1.2 M LiPF ₆ + 0.5% LiBOB + 5% phosphazene in [25/5/70] was used. Moreover, the comparative battery is formed using a cycling process in which the battery is cycled in a standard voltage range of 1.6-2.9V. In contrast, the battery of the present invention is overcharged during the formation process to a state where the anode potential drops below 0.5 V, thereby passivating to the anode by reduction of the additive added to the electrolyte. A layer is formed. The composition and formation process of the comparative battery and the battery of the present invention are listed in Table 3 below.

  16A and 16B show aspects of the comparative battery and the battery of the present invention, respectively. From the swelling of FIG. 16A, it is clear that a significant amount of gas was produced in the comparative battery, while FIG. 16B shows that little or no gas was produced in the battery of the invention. ing.

  Although the present invention has been described herein in a descriptive manner, it should be understood that the terminology used is intended to be the nature of the descriptive terms and not a limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described in the appended claims.

DESCRIPTION OF SYMBOLS 10 Hybrid vehicle or electric vehicle 14 Battery pack 16 Circuit 18 Switch 20 Battery management system 22 Switch management and interface circuit 112 Negative electrode 113,117 Metal current collection material 114 Coating 116 Positive electrode 118 Electrolyte 120 Interface 122 Gas absorbent 124 Separator

Claims (21)

In a method of manufacturing a battery,
A lithium battery having an operating voltage range,
a negative electrode comprising at least a first lithium titanate of the formula Li ₄ Ti ₅ O _12-x , wherein x is greater than 0 and less than ₁₂ .
A positive electrode;
An electrolyte in contact with and between the negative electrode and the positive electrode, the electrolyte comprising an additive;
And a step of forming a coating containing a reduction product of the additive on the interface of the negative electrode in contact with the electrolyte, the lithium battery having a voltage higher than the operating voltage range. Overcharging and lowering the voltage of the negative electrode to the range 0 ≦ V ≦ 1.0 where V is a voltage,
A method comprising:   The method of claim 1, wherein the duration of the forming step is sufficient to produce a continuous coating at the interface.   The method of claim 1, wherein the additive comprises an elemental component selected from the group consisting of boron, phosphorus, sulfur, fluorine, carbon, and combinations thereof. The additive is lithium hexafluorophosphate (LiPF ₆ ), lithium bisoxalate borate (LiBOB), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF) ₃ SO ₃ ), lithium bis (trifluoromethanesulfone) imide (Li (CF ₃ SO ₂ ) ₂ N), lithium tetrafluoroborate (LiBF ₄ ), lithium tetrachloroaluminate (LiAlCl ₄ ), lithium hexafluoroantimonate (LiSbF _6), lithium tetrafluoro (oxalato) phosphate (LiFOP), lithium difluoro (oxalato) borate (LiFOB), Hosufezen, CO _2, phosphate esters, borate esters, and from the group consisting of water It is additive-option, the method of claim 1.   The method of claim 1, wherein the additive comprises at least one chelate borate.   The additive is carbonate, chloroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, sulfite, ethylene sulfite, propane sulfone, propylene sulfite, butyrolactone, phenyl ethylene carbonate, phenyl vinylene carbonate, catechol carbonate, vinyl acetate, dimethyl sulfite, carbonic acid The method of claim 1, comprising an additive selected from the group consisting of fluoroethylene, trifluoropropylene carbonate, bromogammabutyrolactone, fluorogammabutyrolactone, and combinations thereof.   The method of claim 1, wherein the additive comprises lithium bisoxalate borate (LiBOB), phosphazene, or a mixture of both.   The method of claim 1, wherein x is less than 0.02.   The method according to claim 1, wherein an average valence number of titanium in the first lithium titanate is less than 4. 3.   The method of claim 1, wherein the positive electrode comprises lithium titanate.   The method according to claim 1, wherein a lower limit of the operating voltage range is 1.3 V or more. The electrolyte decomposes at a potential of 1.5V to 3.0V lithium;
The method of claim 1, wherein the coating prevents decomposition of the electrolyte at voltages ranging from 0 to 4V. In addition to the first lithium titanate, the negative electrode further comprises a second lithium titanate having the following formula: Li ₄ Ti ₅ O ₁₂ different from the first lithium titanate,
The method of claim 1, wherein the first lithium titanate is present in the negative electrode in an amount greater than the amount of the second lithium titanate.   The said negative electrode contains said 1st lithium titanate at least 10 mass% more than said 2nd lithium titanate based on the total mass of said 1st and 2nd lithium titanate. Method.   The method of claim 1, wherein the lithium battery further comprises a gas absorbent. The method of claim 15, wherein the gas absorbent is selected from the group consisting of ZnO, NaAlO ₂ , silicon, and combinations thereof.   The method of claim 15, wherein the negative electrode comprises the gas absorbent.   The method of claim 15, wherein the lithium battery further comprises a separator, and the gas absorbent is retained by the separator. In a method of manufacturing a battery,
Providing an electrolyte comprising an additive, and a lithium battery,
a negative electrode having a surface coating comprising lithium titanate of the formula Li ₄ Ti ₅ O _12-x , wherein x is greater than 0 and less than ₁₂ , in contact with the electrolyte and comprising a reduction product of the additive;
A positive electrode comprising a mixed oxide type NMC in contact with the electrolyte;
Producing a lithium battery comprising:
A method comprising:   20. The surface coating is formed on the negative electrode by overcharging the lithium battery and lowering the voltage of the negative electrode to the range 0 ≦ V ≦ 1.0 where V is the voltage. the method of. In a method of manufacturing a battery,
Providing an electrolyte having an additive comprising lithium bisoxalate borate (LiBOB) and phosphazene, comprising 0.5% lithium bisoxalate borate (LiBOB) and 5% phosphazene, and lithium battery Because
A negative electrode having a surface coating in contact with the electrolyte, comprising lithium titanate and comprising a reduction product of the additive;
A positive electrode in contact with the electrolyte;
Producing a lithium battery comprising:
A method comprising:

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